Integrated circuit (IC) technologies are constantly being improved. Such improvements frequently involve scaling down device geometries to achieve lower fabrication costs, higher device integration density, higher speeds, and better performance. Along with the advantages realized from reducing geometry size, improvements are being made directly to the IC devices. One such IC device is an image sensor device. An image sensor device includes a pixel array for detecting light and recording intensity (brightness) of the detected light. The pixel array responds to the light by accumulating a charge—the more light, the higher the charge. The charge can then be used, for example, by other circuitry, to indicate a color and/or brightness value, which can then be used for a suitable application such as a digital camera. Common types of pixel arrays include a charge-coupled device (CCD) image sensor or complimentary metal-oxide-semiconductor (CMOS) image sensor device.
One type of image sensor device is a backside illuminated image sensor (BSI) device. BSI devices are used for sensing a volume of light projected towards a backside surface of a substrate (which supports the image sensor circuitry of the BSI device). The pixel array is located at a front side of the substrate and the substrate is thin enough so that light projected towards the backside of the substrate can reach the pixel array. BSI devices provide a high fill factor and reduced destructive interference, as compared to front-side illuminated (FSI) image sensor devices. However, due to device scaling, improvements to BSI technology are continually needed to further improve BSI device quantum efficiency. Accordingly, although existing BSI devices and methods of fabricating these BSI devices have been generally adequate for their intended purposes, as device scaling down continues, they have not been entirely satisfactory in all respects.